Animations Disappear When Loading Up Blender
The F toggle is something many of us animators have complaints about. Yes it has to be selected to keep Actions if you start a new Action. The F toggle stands for Fake User. When you start a new Action via the Action Editor the Action that you had is removed from the Armature. As objects can only use 1 Action at a time.

The correct way to use multiple actions is to use the NLA Editor. There are new buttons in the Action Editor's Header: Push Down and Stash. You can use those to save your Actions in the NLA Editor so that they don't get deleted.